What are some alternatives?
Bill.com - Bill.com provides ACH payments processing, automates your accounts payable and accounts receivable processes.
The Invoice Machine - The Invoice Machine is an online invoicing service with a simple and elegant user interface.
ChargeDesk - ChargeDesk offers billing support across most of the payment service providers.
InvoiceOcean - Create professional invoices in the blink of an eye, InvoiceOcean is efficient and user-friendly!
EasyBill - EasyBill is an online tool for invoicing, stock management and documents management.
Agnitumus Billing System - Billing and Invoicing